TouchDevelop represents a radically new programming environment that enables
users to develop mobile applications directly on mobile devices. TouchDevelop has
successfully drawn a huge number of end users, who have published thousands of
TouchDevelop scripts online. To enhance end-user programming on mobile devices,
we conduct the ﬁrst comprehensive ﬁeld study of 17322 TouchDevelop scripts and
4275 users. Our study consists of an overall study on the characteristics of
scripts (e.g., structural features, code reuse) and users (e.g., expertise), and
a longitudinal study on how they evolve over time. Our study results show
important characteristics of scripts such as dense external method calls, high
code reuse ratio, and also reveal interesting evolution patterns of users. The
ﬁndings and implications in our study provide valuable guidelines for improving
tool support or services for end users and increasing the popularity of end-user
programming on mobile devices.